Code review comment for lp://staging/~abreu-alexandre/webbrowser-app/fix-url-updates-for-manifest-webapps

I updated the TEstPlan to account for those uri-handler tests:

https://wiki.ubuntu.com/Process/Merges/TestPlan/webapp-container

I will update the MR though with tests for that since the matrix of tests is not getting simpler to cover all the cases, it'll be better if automated